Hi, Anonymous you're getting ready to go riding you pull out the dipstick to check your oil level and are greeted with the unmistakable smell of gasoline. What happens next depends on the following:
1. You have experienced this before and do not start the engine but do change your oil and filter leaving it 1 quart low until the engine reaches operating temperature then top off as necessary.
2. The amount of time your bike has been sitting, since the last time the engine was running.
3. The amount of gas and contaminants in the tank.
4. The oil pump location, exterior or interior.
5. The condition of your petcock gasket/seal/diaphragm.
If your gas tank was low and you start the engine probably nothing you would notice but if your gas tank was full and you start your engine the oil/gas mixture can blow into your air filter, come streaming out of your crankcase breather hose, and launch your oil tank cap followed by a blast of oil. The mess can be minor or you need to call a Hazmat team for assistance. This will also happen if you overfill your oil tank.
Next is the how and why gas can get into your oil tank/system:
a. The vacuum petcock rubber/diaphragm fails, which allows gas to flow from the fuel tank through the petcock, through the vacuum line into the intake manifold, then into the combustion chamber, where it seeps past the piston rings and into the bottom end.
3. Non-vacuum petcocks that are not turned to the off position will patiently wait until contaminants from the gas tank build up in between the carburetor needle and seat breaking the seal thus inviting gas to enter the combustion chamber eventually finding it's way into the bottom end and the oil tank.
4. Bottom line if you're not going to ride your bike for a while turn off the petcock.
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sitting is the worst thing for a bike. you have a bad battery. if you have to leave the bike for a long time, put it on a battery tender or at least start it up once a week. the gas will go bad in the fuel system and the battery will fail. also, when you get a battery, make sure to get a good one from the dealer, dont get the cheap ones from walmart or autozone. a factory battery will last 2-5 years. you will be lucky to get 1 year from a cheap battery.

Stock plug is NGK CR9E, but Denso Irridium IU27 is best. Cost more but better economy and starting.
Any manufacturer will have the equivalent NGK plug for your bike on their chart, with two or three types for your preferred riding style.
Cheers.

I would not buy one. It is a water cooled 4 stroke. That part is okay. What is not okay is the fact it has 4 cylinders and is 16 years old. Parts are getting hard to find, dealers generally will not work on a bike more than 10 years old, and because of having 4 cylinders, repairs are EXTREMELY EXPENSIVE. $1200 for a top end job and $1500 for the gearbox. One crummy bent shift fork and you will need to go to the bank. The bike is old enough to be well ready for repairs. Find a 500cc twin cylinder bike 3 to 5 years old and you will save a bunch of cash and still have a rocket. Even if the bike were new I would not buy it due to the 4 cylinders. Please rate my answer. Thanks.

spary wd-40 on all electrical connection that was expossed to water liberally.....if that doesnt do it, then you probably got water in your pulse generator system coils and will have to pull the cover off and see if theres water in there.

that box is called the air box, its where you engine breathes in its air. you say its leaking oil? these boxes are normally a bit oily but only really surface oil. If you can actually see liquid oil you have a problem with your petrol shut off. When the bike isnt running petrol will leak into the engine through the piston. When you start the bike all the petrol mixed with the engine oil will be pumped back into the air box. also check the level of the engine oil, if too much has been put in there then that can also be pumped back into the air box. If the petrol and oil has been mixing you must change the oil as petrol thins the oil and your bike could catch fire, the engine wear will be really bad.

I've had the same problem a couple of times now The fly wheel is located using a 3mm key
which is way to small that shears off putting the timing out causing back firing and not starting.
Mine did it again last weekend so i'm on the search to cure it once and forall.